1. Field of the Invention
The invention relates to a cooling adapter.
2. Description of the Related Art
In an internal combustion engine, with a view to restraining the temperature of a catalyst provided in an exhaust system thereof from rising excessively, it is considered to cool an exhaust gas in the engine by a cooling liquid. In order to realize this cooling of the exhaust gas, as disclosed in, for example, Japanese Patent Application Publication No. 11-49096 (JP-A-11-49096), it is proposed to provide a cooling adapter for exchanging heat between the exhaust gas in the internal combustion engine and the cooling liquid between a cylinder head of the internal combustion engine and an exhaust manifold of the internal combustion engine.
This cooling adapter is so provided between the cylinder head of the internal combustion engine and the exhaust manifold of the internal combustion engine as to connect them together. The cooling adapter is equipped with a plurality of exhaust passages provided in parallel with one another to cause an exhaust gas flowing out from the cylinder head to flow to the exhaust manifold, and a water jacket for causing to flow the cooling liquid that exchanges heat with the exhaust gas flowing through the plurality of the exhaust passages. This water jacket is formed around the entirety of the respective exhaust passages and among the respective exhaust passages. Further, the cooling adapter is also equipped with an inlet portion configured to cause the cooling liquid to flow into the water jacket, and an outlet portion configured to cause the cooling liquid in the aforementioned water jacket to flow out to the outside.
In the aforementioned cooling adapter, the cooling liquid is caused to flow into the water jacket from the aforementioned inlet portion, and the cooling liquid in the water jacket is caused to flow out from the outlet portion. The cooling liquid thereby flows in the water jacket. Then, when the cooling liquid is caused to flow into the water jacket of the cooling adapter while the exhaust gas in the internal combustion engine flows from the cylinder head to the exhaust manifold via the exhaust passages of the cooling adapter, heat is exchanged between the cooling liquid and the exhaust gas flowing through the aforementioned exhaust passages, and the exhaust gas cooled through this heat exchange flows to the exhaust manifold. Accordingly, by providing this cooling adapter, the exhaust gas cooled by the cooling adapter can be sent to a catalyst provided in an exhaust system of the internal combustion engine.
By providing the cooling adapter as described above, the exhaust gas cooled by the cooling adapter can be sent to the catalyst provided in the exhaust system of the internal combustion engine, but the following problem arises inevitably.
That is, that region of the cylinder head of the internal combustion engine on which the cooling adapter is mounted (that region of the cylinder head which is located on an exhaust outlet side) reaches a high temperature due to the heat of the exhaust gas and becomes likely to thermally expand. The cooling adapter must be formed thickly to be able to cope with a stress acting on the cooling adapter as a result of this thermal expansion. Furthermore, as a result of the aforementioned thermal expansion in that region of the cylinder head which is located on the exhaust outlet side, the exhaust gas is likely to leak from a gap between mating faces of the cylinder head and the cooling adapter. Therefore, in order to suppress this leakage, it is necessary to take a measure such as the provision of a plurality of gaskets between the mating faces or the like.
Further, in the aforementioned cooling adapter, since the plurality of the exhaust passages are provided in parallel with one another, the cooling liquid in the water jacket is unlikely to flow into regions among the plurality of the exhaust passages. As a result, heat is unlikely to be exchanged between the cooling liquid and the exhaust gas in the regions among the plurality of the exhaust passages in the water jacket, and the efficiency of cooling the exhaust gas by the cooling adapter decreases correspondingly.